Information
Enables a remote user to log on to this computer and run programs, and supports various TCP/IP Telnet clients, including UNIX-based and Windows-based computers.
The recommended state for this setting is: 'Disabled' or 'Not Installed'.
Note: This service is not installed by default.
It is supplied with Windows, but is installed by enabling an optional Windows feature (_Telnet Server_).
Rationale:
Hosting a Telnet server (especially a non-secure Telnet server) from a workstation is an increased security risk, as the attack surface of that workstation is then greatly increased.
Note: This security concern applies to _any_ Telnet server application installed on a workstation, not just the one supplied with Windows.
Solution
To establish the recommended configuration via GP, set the following UI path to: 'Disabled' or ensure the service is not installed.
Computer Configuration\Policies\Windows Settings\Security Settings\System Services\Telnet
Impact:
Remote user Telnet access will not be available.